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Hi.
Recently been getting out with a mate when he's home from the armed forces, as he rides more road than mtb I decided to buy a giant defy so at least when we get out, we could alternate riding type
However, the defy is used, everything looks in very good well serviced condition. The original owner said it was used on rollers and never had it on the road. It doesnt look like its done many, if any road miles.
The problem I'm having is on when on the small sprocket on the front triple chainset. When in the first few gears everythings fine, then when I get to the last 3 gears on the cassette I noticed a loud metal on metal sound. I put it on the stand and can see the chain is rubbing against the middle chainring when on those 3 cogs of the cassette
I can't see if somethings been replaced and that's what's causing it. Could the middle ring or small ring have been replaced for a ring with a different o/d??
Any ideas what's wrong?
Cheers
Steve
You aren't really supposed to run the gears like that, with the chain crossed from the small chainring to the small sprockets. The middle chainring is the general purpose gear so it should run fine on all gears on the cassette. The small chainring is intended for climbing stuff that's too steep for the middle ring so it should run fine on the largest 4 or 5 sprockets, but it's not intended to run on the smallest sprockets (you should have changed up to the middle chainring if you're going that fast). The large chainring should run fine on the smallest 4 or 5 sprockets, but if you need to use the larger sprockets, you should have dropped down to the middle chainring first.
That's exactly what it does. It runs fine in the middle ring on all sprockets on the cassette
I ran the bike up the road checking everything worked, I understand I would be normally have changed up to the middle ring by then but it just seemed a bit extreme. I've not had many road bikes but I can't say I've ever had the chain do this on any bike to this extent that I've noticed. At worst it's been the chain against the front derailer as apposed to the chain against the middle chain ring.
Ok, I'm a able to get round it cos exactly as you say I tend change before the problem occurs and only need the small ring when climbing
I just wanted to make sure I wasn't missing something obvious...
Cheers
Its called cross chaining, its not designed to work like that, some bikes are worse than others depending on chainline, components etc. You basically want to keep the chain as straight as possible.
Great. Thanks for the diagram. That's exactly how it is but it just seemed a bit excessive to me! ...
I understand about chain line but this is the worst I've seen over my 40 years cycling.
Thanks again
I don't experience this on my ancient 3x9 XT Octalink set up and can ride any gear combination without issue except for a bit of front mech. rub whilst in the granny ring and top two cogs (I do occasionally use the bail out gears). The only time I've experienced anything akin to this was when I fitted a Middleburn Hardcoat outer ring to an identical chainset. The hardcoat ring was noticeably thicker than the Shimano ring it replaced and if I rode the top couple of cogs whilst in the middle ring, the chain would rub the outer ring; the shifting pins on the Middleburn would also lift, then drop, the chain from the middle ring.
Just wondering if ring thickness might be an issue.
I've encountered this in the past when trying to fit the smallest compatible granny ring to a road triple crank.
Not sure what kind of bottom bracket you have, however if there's a spacer on the left (non drive side) try swopping it over to the drive side.
If it's square taper / splined you can increase the width of the BB which will also work.
In my case this worked: By increasing the size of the granny ring (smallest front chain ring). You could also reduce the size of the middle ring, or adjust both for a compromise.
If the cranks and chain rings came stock on the bike however, this seems like a really poor choice to go with the frame.
BTW: I have worked on lots of different bikes, own a fair few and have ridden many more. It's not advisable for chain and ring wear, however you should be able to 'cross chain' without this happening.
I rarely use more the the 4 inner (biggest) sprockets in the granny ring for this exact reason), the chain angle is too much and it usually catches the front mech first.
Same for the big ring, I never go more than halfway up the block.
The chain does lift and almost ramps up onto the middle ring. As bigyinn and pjay state its usually just the front mech in my experience that catches.
Yeah binno that's what I thought.... I should be able to cross chain (although I wouldn't intentially when riding normally) without this being so extreme, front mech rub I'd expect!
It's a square taper, I can't see a spacer on either side!
Could the chain have been changed and a 6/7 speed chain used, instead of the correct speed chain. I assume that the chain in that case would
Be too thick and the source??? Is there an easy check for this? Chain dimensions???
Looks like I might take some time at the weekend to strip, inspect and take some measurements
Thank guys..
Doctor, it hurts when I move my arm like this.
Don't move your arm like that then.
Don't cross your chain, you're not supposed to.
...well its what i always think of to remind me or teach my kids
dump the triple, get a double, lighter and not as many issues with chain line.
What gets me on road bikes is the plethora of trimming options - it took me a good while to realise my campag stuff wasn't meant to be trimmed on the big ring, which explained why it was really difficult to do so without shifting down to the small ring!
Wider BB might alleviate the problem, but will make your chainline worse in the outer ring - and everyone knows you should be using the outer ring for everything regardless to show what a hardman you are (until you're doing 25RPM with the chain crossed up in big/big).
So long as you comply with THE RULES.
I'd hazard a guess that you have 21 "real world" gear combinations at best without extreme chainline angles...
Avoid two smallest sprockets in granny ring
Avoid biggest and smallest in middle ring
Avoid biggest two sprockets in big ring
Having said that, I've heard that middle rings on triples give a good chainline for 1x narrow/wide rings, so you might be able to use the whole cassette block with it and have 23 gear combos.
Is the stop screw on the front mech possibly not screwed in enough meaning the front derailleur sits too far to the left?
Check your chainline with the current bottom bracket. You can do this the right way, or simply put the chain in the middle front ring and middle rear cog and eye ball it for how straight the chain looks from the rear of the bike.
This will give you an indication of far over you can move the crank with a longer bottom bracket. You can go a little more than dead centre and it will be fine btw.
Also, you can use a 10 speed chain on a 9 speed cassette which will be as flexible as you'll get chain wise.
Also check that your front mech is on the correct position + height from the largest chain ring. Also check to see that the front mech is the correct model for the size of the largest ring used, as they are quite specific. Giant should have the original spec listed online somewhere.
You definitely be able to improve on where it is now.
Thanks binno.
Cheers guys.
You know what I'm glad I posted! I never thought that maybe "just don't do it"...... Thanks for that!